This invention relates to electrochemical cells and batteries and means for improving vibration resistance.
Electrochemical cells and batteries are oftentimes subjected to thrusts and vibrations along various axes of the cell or battery. Cells are particularly susceptible to vibration or rotation tending to displace the cell pack of electrode plates and interleaved separators, placing the current collector tab and strap connections in stress normally lengthwise of the plates and in the direction of the respective interconnections, i.e., axially in the case of a cylindrical wound cell. It has been found that severe vibration will cause stress cracking particularly in the strap connecting the output terminal post to current collector tabs of the plates, leading to eventual loss of the electrical connection. Crack initiation and propagation is particularly severe in high purity lead straps, and current collector tabs integral with the plate grids, such as the high purity type taught in U.S. Pat. No. 3,862,861 to McClelland et al.
One attempt to solve this problem entailed crimping (indenting) the container to immobilize the cell pack but this created additional problems such as an increased tendency to fail by short-circuiting.